Add UV Mapped texture coordinates to OBJ file?
If you want texture coords when exporting to .obj, make sure you have Include UVs ticked in the exporter options (it should be checked by default). Also, make sure that you actually unwrapped the model, check UV Maps under Data in the Properties panel to make sure that a UV map is assigned to your object.



If you should open an obj file you should see something like 

vt 0.000100 0.000100
vt 0.999900 0.000100
...
f 1/1 2/2 4/3 3/4


where the lines with vt are texture coordinates and the line(s) with f specify faces that are a part of the UV map. Read more on the obj format here. That being said, it is an open format and people might roll their own custom exporters and importers and name these identifiers differently (not recommended). I know that g is used by default for groups so you might be looking in the wrong place, also if you have a texture with the model make sure their is a .mtl file along with the obj to ensure that everything works correctly.